21' Scarab Prop Selection
 

Hey guys, struggling to find a starting point to select a prop. 1985 Scarab 1 21' 3200lbs dry ~4000 loaded. BBC 560hp@5200 630tq@4100 bravo 1 drive, wide trim tabs

Picked up the boat last year with stock 454 330hp mag w/ alpha 1 - I never ran the boat so I don't have a baseline for comparison. Came with a 21" 4 blade. New to I/Os and am clueless which prop to start with - I know it is mostly trial and error but need a starting point. Reached out to bblades a couple weeks ago with no answer, I'm assuming they are pretty busy this time of year

I was thinking a bravo FS 26" but thinking maybe 28-30" would be more suitable for my weight/power? Not looking for every last MPH, an all around one would be great. Diameter? Pitch? Blade #? Any suggestions welcome, thanks!

I think the short tube on the FX will not give enough stern lift to get the entire boat up out of the water making it sluggish and excessive slip.

That is a fair assumption, I was wondering if the short tube would hurt overall performance - do you have a better prop in mind?

What outdrive ratio? Assuming 1.50:1?
If so, I think you might be surprised how much power a 26" Rev 4 will soak up. IMHO that would be a good starting point. Maybe a 25" Mirage Plus but you'd likely hit the rev limiter with that. The ***** of it all is...props are still hard to find, generally speaking. A few months ago it was a year wait for new props from Mercury.

Checkmate,

Try a Bravo28 to start with. You're 1600lbs lighter than I am, and that's what I'm pulling with what I'd guess is similar power (ProCharged 496HO). I'm gonna guess you're gonna be in a 30 or maybe even a 32 before you're properly loaded.

Thanks. Brad.
(937)545-8991

You are correct, 1.5 ratio drive - and so ive found out! props are getting few and far in between but thankfully I have another couple of months to search

Thanks Brad, I figured it would start to inch up into that range, I am going to keep my eye out for a bravo 28 and see if I can snag one up. It seems like the best all around prop without much compromise

Checkmate,

Not knowing anything about your hull, and just going buy weight, I’m betting you’ll bury the rev limiter with a B28.

Keep your eye out. A B28 just popped up and sold here on OSO. Post in the “Wanted” section you’re looking for one. You might be surprised.

One more thing…. I hope you upgraded the outdrive….

Thanks. Brad.
(937)545-8991

I hope you installed external hydraulic steering! It will be a must in a small hull with that power level. Will be very hard to control any chine walk and properly balance the hull on the keel without it.

Small light fast boat, i don’t see stock outdrive being an issue. These are quick/fast without lots of power.

Speaking of which, did some history digging and saw where 500hp puts these boats near/at 80. Found a 383 near 500hp and a 525efi as example.

I don’t know these with bigger motors, I just work on a bone stock Scarab 1 with 260hp alfalfa 1.47 drive. Swings a 21” cleaver no issue unless overloaded with peeps and coolers. Then will throw a 19” on it. Either way, boat needs tabs to plane better.

I’d start with a 28” bravo , you may not want to go faster anyway ? I dunno.


https://cimg5.ibsrv.net/gimg/www.off...da24aa37d.jpeg

SB,

I had a B26 on our PQ while the injectors were giving us fits. After getting them straightened out, we took the boat to the lake to test them out. I couldn't get much above 2/3, maybe 3/4 throttle without bumping the rev limiter. When I reacquired a B28, I can now bury the fun stick and the engine loads out right at 5K RPM.

I'd much rather not be able to use the top end of the throttle range because my knuckles can't get any whiter, rather than because I'm afraid of a rod through the side of the block. Just sayin'... :ernaehrung004:

I didn't catch that the OP had upgraded to a Bravo drive. I thought he was still running the Alpha. All good.

Thanks. Brad.
(937)545-8991